1. Field of the Invention
The invention relates to wire feed sensor guides used in semiconductor package fabrication. More specifically, the invention relates to wire feed sensor guides that are of a simple (for example, unitary) construction, and thus are easily replaceable and serviceable by operators or technically unskilled individuals.
2. Related Art
Wire feed sensor guides are known in the art of semiconductor package fabrication. Such guides feed wire to a capillary in order to bond lengths of the wire between points in a semiconductor package. Semiconductor package fabrication systems typically include a motor to which a spool of the wire is attached, an eyelet through which the wire passes before entering the sensor guide, an air tensioner for controlling an amount of tension present in the wire extending from the spool to a wire clamp that is disposed between the tensioner and the capillary.
One conventional wire feed sensor guide includes a wire sensor, an air pressure inlet, and two guide plates separated by a shim plate. The sensor is adjusted to be aligned with a path of the wire, and is locked in place. The guide plates guide the wire so that the wire can be controlled to be within sensor range, the wire location being controlled in part by air pressure from the air pressure inlet.
This conventional wire feed sensor guide arrangement has several disadvantages. To remove the assembly for cleaning or other maintenance, two tiny screws have to be removed and the assembly has to be taken apart in three pieces (the two closely-spaced guide plates and shim). Removing the screws releases all three pieces simultaneously, which often causes damage or loss.
The pieces are difficult to replace properly and adjust accurately. After being repaired or cleaned, the parts cannot readily be easily re-assembled and reliably set in their original positions, especially by those individuals not having specialized training and skills. Improper re-assembly causes such issues as the wire becoming kinked or stuck, or simply fluttering rather than being smoothly fed along a desired path.
Moreover, in this conventional arrangement, the wire sensor is exposed to dust and other elements, the wire position sensing thus becoming less reliable and causing the overall wire bonding operation to be sluggish. Given the structure of the conventional wire feed sensor guide, in which the sensor is difficult to remove and clean, the susceptibility of the wire sensor to contamination adds to the problems described above.
The frequency of defects and stoppages caused by this conventional wire feed sensor guide is very high. Moreover, maintenance often causes damage to the assembly, which in turn causing deterioration in MTBA (mean time between assists; a reliability measure based on an average time between assists required to maintain equipment). In any event, most operators cannot safely perform simple maintenance, and have to depend on technicians or other individuals having specialized skill and training.